1. Technical Field
The present invention relates to a method for operating a wind power plant, wherein the wind power plant has a multiplicity of components but at least one rotor having at least one rotor blade and a generator for converting the mechanical energy of the rotor into electrical energy, wherein one or more characteristics are determined, particularly measured, which are directly or indirectly dependent on forces acting on the component and/or conversely depend on these forces acting on the component such as, for instance, the current wind speed or an operating parameter of the wind power plant, for instance the wind angle of attack of the rotor blade. The present invention also relates to a wind power plant for carrying out the method.
2. Related Art
Various components of a wind power plant are subject to different actions of force. These actions of force, in turn, lead to different problems. For example, the rotor blades of a wind power plant are exposed to a high wind load. The forces due to the wind load predominantly produce a deformation of the rotor blades. This deformation is usually greater at the wing tips than in the rotor blade sections closer to the rotor center.
Among other things, the blade deformation affects the angles of attack of the rotor blades with respect to the wind, set in each case. The actual angle of attack therefore frequently deviates from the predetermined angle of attack, particularly towards the blade tips. To counteract this, it is known in the prior art to prebend the rotor blades forward during its production, i.e. into the direction facing the wind with respect to the installed state. This predetermined prebending is a compromise, however, because it is only at a particular wind speed that the ratios of forces are such that the prebending in the production exactly compensates for the deformation caused by the wind pressure. When wind velocities deviate from this, the position of the rotor blade with respect to the wind is not optimal, therefore.
The forces influencing the individual components of the wind power plant such as, for example, the wind load, the respective inherent weight of the components or the like do not only lead to aerodynamic problems. In addition, these forces, particularly cyclic loads, also have a negative effect on the life of the individual components.
From US Patent Publication No. 2004/0067134 A1, it is known to twist rotor blades about their longitudinal axis in dependence on the wind speed measured, i.e. to partially turn or pitch the rotor blades out of the wind. For this purpose, piezoelectric fibres, the lengths of which can be controlled via a control device, are arranged within the walls of the rotor blade. As part of the solution of this document, the result is that the production of some forces having a negative influence on the rotor blade is already partially prevented in a relatively complicated manner in that the rotor blade is turned out of the wind in dependence on the intensity of the wind. The disadvantageous factor in this solution is, however, that naturally, it is not possible to prevent a multiplicity of forces acting on the rotor blade and having a negative influence on being produced. These forces which cannot be inhibited in advance by means of the partial pitching and which thus act on the rotor blade can continue to have a negative effect and damage the rotor blade in the context of the solution of US Patent Publication No. 2004/0067134 A1.